Lateral force control is implemented through any of a number of automatic vehicle control systems including electronic power steering systems (EPS), collision imminent systems (CIS), lane centering systems, electronic stability control (ESC) systems, comprehensive safety vehicle (CSV) systems, and vehicle lane change assist systems. Prevention of operating in an unstable region of the tire, when tire lateral force is excessive, allows for effective operation of such vehicle control systems.
Tire saturation or lateral force tire saturation is one parameter used as an indicator of lateral stability of a vehicle and is used in some vehicle control systems. Tire saturation refers to an unstable region, whereby a usually substantially linear relationship between tire lateral force and slip angle ceases and the tire exhibits a lack of responsiveness to further steering force. Tire slip angle is an angle between a rolling wheel's actual direction of travel (heading direction of the vehicle) and the direction towards which the wheel is pointing. Lateral (i.e., parallel to the wheel axle) force is a force produced by a vehicle tire during cornering and is linearly proportional to slip angle at low and moderate slip angles. However, as slip angle increases, lateral force peaks at a lateral tire saturation force, beyond which steering control is unstable. Some vehicle control systems operate to keep lateral force within a stable region of low and moderate slip angles.
Accordingly, the need exists for a system and method for determining lateral tire force saturation. In addition, it is desirable to provide such systems and methods without requiring parameters that are complex to estimate, such as road condition, and in a processing efficient scheme. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.